1. FIELD OF THE INVENTION
The present invention relates to a presensitized lithographic printing plate processing apparatus for processing a presensitized lithographic printing plate requiring no damping water (which will be referred to as a waterless presensitized lithographic printing plate or a waterless PS plate hereinafter) having an image exposed thereon.
2. DESCRIPTION OF THE PRIOR ART
Waterless PS plates with a silicone layer as an ink repellent layer which have been proposed include a first type having a photo-solubilizable or insolubilizable, photo-sensitive layer and a silicone rubber layer laminated on a substrate, (described in Japanese Patent Publication Nos. 23042/69 and 16044/71), and a second type having a photo-adherent, photo-sensitive layer and a silicone rubber layer laminated on a substrate, (described in Japanese Patent Application Laid-open Nos. 94504/73 and 50102/75). Several tens of thousands of prints can be made using these waterless PS plates without using damping water.
In the former case, the solubilization or insolubilization of the photosensitive layer by exposure provides the negative-type or positive-type printing plate. In a developing process of such a waterless PS plate, the exposed area of the photo-sensitive layer of the photo-solubilization type waterless PS plate or the unexposed area of the photo-sensitive layer of the photo-insolubilization type waterless PS plate is dissolved by water, alcohol or the like, and the silicone rubber layer in an image area is rubbed off thereby exposing the hydrophilic printing substrate to provide a negative type or positive type printing plate.
In such process, however, the silicone rubber layer is forcedly peeled off by rubbing with a brush or the like, while applying the developing solution. Hence, the silicone rubber layer which should remain as a non-image area on the surface of the PS plate may be damaged.
On the other hand, in the processing of a the second type of waterless PS plate, the silicone rubber layer in the unexposed area is selectively peeled off by use of a developing solution capable of swelling only the silicone rubber layer without substantially dissolving the photo-adherent, photo-sensitive layer, by utilizing the fact that the photo-adherent, photo-sensitive layer and the silicone rubber layer are firmly photo-adhered by exposure.
When such developing process is used, the good peeling characteristics of the silicone rubber layer provide a sharp dot edge as compared with the former example. But development requires a long time because of the relatively large interfacial adhesion force between the silicone rubber layer and the photo-adherent, photo-sensitive layer in the unexposed area. Moreover, in order to obtain a very small dot in a high-light area with a good reproducibility, it is necessary to rub the plate surface with a relatively strong rubbing force. Thus, it is difficult to completely overcome the disadvantage that even the silicone rubber layer which should remain as a non-image area on the plate surface is liable to be damaged.
A developing process has been proposed in Japanese Patent Publication No. 33140/88, which comprises eluting a portion or the whole of the photo-sensitive layer in the image area with a processing solution capable of dissolving a portion or the whole of the photo-sensitive layer in the image area, and then peeling off the silicone rubber layer in the image area by rubbing the plate surface in the presence of water of a water-based solvent incapable of swelling the silicone rubber layer.
However, this developing process is accompanied by the problem of a need for a long developing time. This is because the development comprises the two steps of eluting a portion or the whole of the photo-sensitive layer in the image area and peeling off the silicone rubber layer with water or an aqueous solvent incapable of swelling the silicone rubber layer.
Another problem is that the developing process comprises the two steps which require developing tanks for each step. Further, a dyeing tank for the dyeing process for the inspection of the plate after processing may be disposed downstream of the developing tank, resulting in a large-sized processing apparatus.
A further problem is there is the need for a feeder for supplying water or an aqueous solvent onto the plate surface in addition to the developing solution for eluting a portion or the whole of the photo-sensitive layer in the image portion, a pipe or the like between such feeder and the developing tank resulting in a complicated apparatus.